Heathrow resumed flights, a spokeswoman for Europe's biggest airport said, after departures were disrupted for an hour on Tuesday following reports of a drone sighting. "We apologize to passengers for any inconvenience this may cause".
Passengers who were stuck at Heathrow expressed their frustration at having to wait to depart while the airport responded to the sighting.
All departures were stopped "as a precaution" shortly after 5pm, leaving passengers stranded on the runway just weeks after a similar debacle caused chaos at Gatwick.
Sussex Police Chief Giles York, who is working on the Gatwick investigation, told BBC radio in late December that police have searched 26 potential launch sites near the airport but do not believe they have found the drone that was seen near the runway on Dec. 19 and Dec. 20.
"Sitting on a plane at #Heathrow".
John Stewart, of the Heathrow noise reduction campaigning group Hacan, said: "Although a third runway will clearly bring many losers, one long-lasting impact of these proposed changes is that a break from aircraft noise would be guaranteed to many more people than who now enjoy it, as Heathrow would make the biggest changes to its flight paths since opening in 1946".
British officials used sophisticated military gear to get Gatwick back in operation, and aviation authorities said that equipment could be deployed at other British airports to deter drone intrusions.
Meanwhile, UK government introduced new police powers against drones flown near airports this week.
The alleged sighting came four days after both Heathrow and Gatwick airports reported they were investing millions of pounds in equipment to prevent future flight disruption. No arrivals, no departures due to Drone activity in the area'.
The exclusion zone around airports will be extended to approximately a three-mile radius, with extensions from runway ends.
Fines of up to £100 could be given for offences such as failing to comply with a police officer when instructed to land a drone, or not showing their registration to operate a drone.